Yes there is - or at least there was on mine. I think there should have been some kind of a valve in the hole but I just siliconed it up. Not sure what the hole was there for - to drain any water that gets in maybe? I found out about the hole when I found a little water in the box after a water crossing - and I think it was water that was splashed up rather then water flooding in because of depth. Anyway, the hole has been sealed up for years now with no problem. Just the same, I would avoid water that is deeper than the height of the tyres.